diff --git a/TODO b/TODO
index 7c300f0..9a8fa8a 100644
--- a/TODO
+++ b/TODO
@@ -1,4 +1,4 @@
-Individual device control
+#Individual device control
 List devices
 Query backlight percentage (get)
 allow fade in and fade out
diff --git a/makefile b/makefile
index 70b1a3a..7d6cb2e 100644
--- a/makefile
+++ b/makefile
@@ -2,7 +2,7 @@
 all: rexbacklight
 
 rexbacklight: src/rexbacklight.c
-	gcc -std=c11 -g -Wall -Wextra -pedantic src/rexbacklight.c -o rexbacklight
+	gcc -std=c11 -DDEBUG_REXBACKLIGHT -g -Wall -Wextra -pedantic src/rexbacklight.c -o rexbacklight
 #	strip --strip-all rexbacklight
 
 .PHONY: install
diff --git a/src/rexbacklight.c b/src/rexbacklight.c
index 29b63b9..45d60ee 100644
--- a/src/rexbacklight.c
+++ b/src/rexbacklight.c
@@ -24,8 +24,6 @@
 #include <dirent.h>
 #include <errno.h>
 
-#define OP_INC 1
-#define OP_DEC 2
 #define OP_SET 4
 #define OP_GET 128
 #define OP_NONE 0
@@ -41,8 +39,40 @@
 
 #define CHECK_OPTION(opt, arg) (!strcmp(opt##_LONG_OPT, arg) || !strcmp(opt##_SHORT_OPT, arg))
 
+#define RETVAL_INVALID_FILE        -1
+#define RETVAL_INVALID_DIR         -2
+#define RETVAL_UNRECOGNIZED_OPTION -3
+#define RETVAL_MISSING_OPTION      -4
+#define RETVAL_INVALID_DEVICE      -5
+#define RETVAL_SUCCESS              EXIT_SUCCESS
+
+struct string_array{
+	char** list;
+	int size;
+};
+
+struct arg_values{
+	struct arg_values* next;
+
+	//Specific device to control
+	//NULL means all devices
+	const char* device;
+
+	//What value to put in the backlight file
+	char* delta;
+
+	//How many seconds to transition
+	int fade_duration;
+
+	unsigned char operation;
+};
+
+
+
 //This is where backlight devices can be found in sysfs
 static const char* backlight_dir = "/sys/class/backlight/";
+static const char* backlight_file = "brightness";
+static const char* max_backlight_file = "max_brightness";
 
 //Print out usage message and GPL message if not caused by an error
 void usage(int exit_val){
@@ -56,7 +86,7 @@ void usage(int exit_val){
 	fprintf(stderr, "  max\n");
 	fprintf(stderr, "  min\n");
 
-	if(!exit_val){
+	if(exit_val == RETVAL_SUCCESS){
 		fprintf(stderr, "\nrexbacklight Copyright (C) 2018 rexy712\n");
 		fprintf(stderr, "This program comes with ABSOLUTELY NO WARRANTY.\n");
 		fprintf(stderr, "This is free software, and you are welcome to redistribute it\n");
@@ -67,79 +97,116 @@ void usage(int exit_val){
 	exit(exit_val);
 }
 
-struct string_array{
-	char** list;
-	int size;
-};
+void free_cmd_args(struct arg_values* a){
+	if(!a->next)
+		return;
+	free_cmd_args(a->next);
+	free(a->next);
+}
 
-//Get a list of backlight devices in sysfs
-struct string_array get_backlight_sources(void){
+#define CHECK_NEXT_ARG(rval) \
+	do{ \
+		if(i == argc - 1){ \
+			fprintf(stderr, "Missing argument to '%s'\n\n", argv[i]); \
+			free_cmd_args(&ret); \
+			usage(rval); \
+		} \
+	}while(0)
+#define UNRECOGNIZED_OPTION(rval) \
+	do{ \
+		fprintf(stderr, "Unrecognized command line option '%s'\n\n", argv[i]); \
+		free_cmd_args(&ret); \
+		usage(rval); \
+	}while(0);
 
-	DIR* fd;
-	struct dirent* dir;
+//Convert command line arguments to flags
+struct arg_values process_cmd_args(int argc, char** argv){
+	struct arg_values ret = {0};
+	struct arg_values* curr = &ret;
 
-	fd = opendir(backlight_dir);
-	//If the dir can't be opened, return no backlight devices
-	if(!fd){
-		fprintf(stderr, "Unable to open '%s' for reading!\n", backlight_dir);
-		return (struct string_array){.list = NULL, .size = 0};
-	}
+	//Skip argv[0]
+	for(int i = 1;i < argc;i++){
 
-	int i, list_size = 8;
-	char** list = malloc(sizeof(const char*) * list_size);
+		//Check for switches
+		if(CHECK_OPTION(GET, argv[i])){
+			curr->operation |= OP_GET;
+			continue;
 
-	for(i = 0;(dir = readdir(fd));){
-
-		//Resize list if more than 8 backlight devices exist (not likely)
-		if(i > list_size){
-			char** tmp = malloc(sizeof(const char*) * (list_size += 8));
-			for(int j = 0;j < i;j++){
-				tmp[j] = list[j];
-			}
-			free(list);
-			list = tmp;
-		}
-
-		//Don't include "." or ".." in directory list
-		if(!strcmp(dir->d_name, ".") || !strcmp(dir->d_name, "..")){
+		}else if(CHECK_OPTION(FADE, argv[i])){
+			CHECK_NEXT_ARG(-5);
+			curr->fade_duration = strtol(argv[++i], NULL, 0);
 			continue;
 		}
-		list[i] = malloc(strlen(dir->d_name) + 1);
-		strcpy(list[i], dir->d_name);
-		i++;
+
+		else if(CHECK_OPTION(DEVICE, argv[i])){
+			CHECK_NEXT_ARG(-5);
+			curr->next = calloc(1, sizeof(struct arg_values));
+			curr = curr->next;
+			curr->device = argv[++i];
+			continue;
+		}
+		else if(CHECK_OPTION(HELP, argv[i])){
+			free_cmd_args(&ret);
+			usage(RETVAL_SUCCESS);
+		}
+
+		else if(!strcmp(argv[i], "max")){
+			curr->operation = OP_SET;
+			curr->delta = argv[i];
+		}
+		else if(!strcmp(argv[i], "min")){
+			curr->operation = OP_SET;
+			curr->delta = argv[i];
+		}
+		else if(!strcmp(argv[i], "off")){
+			curr->operation = OP_SET;
+			curr->delta = argv[i];
+		}
+
+		//If we get a '-' followed by not a number, it's not a known option
+		else if(argv[i][1] < '0' || argv[i][1] > '9'){
+			UNRECOGNIZED_OPTION(RETVAL_UNRECOGNIZED_OPTION);
+		}
+
+		//If we get a '-' followed by a number, it's a decrement request
+		else{
+			curr->operation = OP_SET;
+			curr->delta = argv[i];
+		}
 	}
 
-	closedir(fd);
+	//If there isn't an operation defined in the global context and there is no specified device, there's nothing to do
+	if(!ret.operation){
+		if(!ret.next){
+			fprintf(stderr, "No operation requested!\n\n");
+			usage(RETVAL_MISSING_OPTION);
+		}
+		//if there is a device specified, make sure each one has a requested operation
+		for(curr = ret.next;curr;curr = curr->next){
+			if(!curr->operation){
+				fprintf(stderr, "No operation requested for device '%s'!\n\n", curr->device);
+				free_cmd_args(&ret);
+				usage(RETVAL_MISSING_OPTION);
+			}
+		}
+	//If there is a globally defined operation, apply it to the devices with no operation request
+	}else{
+		for(curr = ret.next;curr;curr = curr->next){
+			if(curr->operation == OP_NONE){
+				curr->operation = ret.operation;
+				if(!curr->delta)
+					curr->delta = ret.delta;
 
-	return (struct string_array){.list = list, .size = i};
-}
-
-//Delete the list of backlight devices
-void free_string_array(struct string_array* s){
-	for(int i = 0;i < s->size;i++)
-		free(s->list[i]);
-	free(s->list);
-}
-
-//Read a float from a file
-float get_brightness(const char* file){
-	//Static buffer because it shouldn't be able to exceed 127 chars long
-	char buff[127];
-	FILE* bright = fopen(file, "r");
-	if(!bright){
-		fprintf(stderr, "Unable to open brightness file \"%s\"!\n", file);
-		return 0;
+			}
+		}
 	}
-	if(!fgets(buff, sizeof(buff), bright)){
-		fprintf(stderr, "Unable to read file \"%s\"!\n", file);
-		fclose(bright);
-		return 0;
-	}
-	fclose(bright);
-	return atof(buff);
+	return ret;
 }
+#undef CHECK_OPTION
+#undef UNRECOGNIZED_OPTION
 
-int process_arg(char* arg, float min, float current, float max){
+//Process an operation
+int process_op(char* arg, float min, float current, float max){
 	//Amount to inc/dec
 	int delta = delta = max * atof(arg + 1) / 100.0;
 
@@ -180,180 +247,169 @@ int process_arg(char* arg, float min, float current, float max){
 	//Set to maximum
 	}else if(!strcmp("max", arg)){
 		return max;
-	//Unknown option
-	}else{
-		usage(-1);
 	}
 	return current;
 }
 
-struct arg_values{
-	struct arg_values* next;
+//Delete the list of backlight devices
+void free_string_array(struct string_array* s){
+	for(int i = 0;i < s->size;i++)
+		free(s->list[i]);
+	free(s->list);
+}
 
-	//Specific device to control
-	//NULL means all devices
-	const char* device;
+//Get a list of backlight devices in sysfs
+struct string_array get_backlight_sources(void){
 
-	//What value to put in the backlight file
-	int delta;
+	DIR* fd;
+	struct dirent* dir;
 
-	//How many seconds to transition
-	int fade_duration;
+	fd = opendir(backlight_dir);
+	//If the dir can't be opened, return no backlight devices
+	if(!fd){
+		fprintf(stderr, "Unable to open '%s' for reading!\n", backlight_dir);
+		return (struct string_array){.list = NULL, .size = 0};
+	}
 
-	unsigned char operation;
-};
+	int i, list_size = 8;
+	char** list = malloc(sizeof(const char*) * list_size);
 
-void free_cmd_args(struct arg_values* a){
-	if(!a->next)
+	for(i = 0;(dir = readdir(fd));){
+
+		//Don't include "." or ".." in directory list
+		if(!strcmp(dir->d_name, ".") || !strcmp(dir->d_name, "..")){
+			continue;
+		}
+
+		//Resize list if more than 8 backlight devices exist (not likely)
+		if(i > list_size){
+			char** tmp = malloc(sizeof(const char*) * (list_size += 8));
+			for(int j = 0;j < i;j++){
+				tmp[j] = list[j];
+			}
+			free(list);
+			list = tmp;
+		}
+
+		list[i] = malloc(strlen(dir->d_name) + 1);
+		strcpy(list[i], dir->d_name);
+		i++;
+	}
+
+	closedir(fd);
+
+	return (struct string_array){.list = list, .size = i};
+}
+
+
+//Read a float from a file
+float get_brightness(const char* file){
+	//Static buffer because it shouldn't be able to exceed 127 chars long
+	char buff[127];
+	FILE* bright = fopen(file, "r");
+	if(!bright){
+		fprintf(stderr, "Unable to open brightness file \"%s\"!\n", file);
+		return 0;
+	}
+	if(!fgets(buff, sizeof(buff), bright)){
+		fprintf(stderr, "Unable to read file \"%s\"!\n", file);
+		fclose(bright);
+		return 0;
+	}
+	fclose(bright);
+	return atof(buff);
+}
+
+//Write value to backlight files
+void write_delta(char* delta){
+	int out = process_op(delta, 0, get_brightness(backlight_file), get_brightness(max_backlight_file));
+	FILE* bright = fopen(backlight_file, "w+");
+	if(!bright){
+		fprintf(stderr, "Unable to open brightness file \"%s%s\" for writing!\n", backlight_dir, backlight_file);
 		return;
-	free_cmd_args(a->next);
-	free(a->next);
-}
-
-#define CHECK_NEXT_ARG(rval) \
-	do{ \
-		if(i == argc - 1){ \
-			fprintf(stderr, "Missing argument to '%s'\n\n", argv[i]); \
-			free_cmd_args(&ret); \
-			usage(rval); \
-		} \
-	}while(0)
-#define UNRECOGNIZED_OPTION(rval) \
-	do{ \
-		fprintf(stderr, "Unrecognized command line option '%s'\n\n", argv[i]); \
-		free_cmd_args(&ret); \
-		usage(rval); \
-	}while(0);
-
-struct arg_values process_cmd_args(int argc, char** argv){
-	struct arg_values ret = {0};
-	struct arg_values* curr = &ret;
-
-	//Skip argv[0]
-	for(int i = 1;i < argc;i++){
-
-		//Check for switches
-		if(CHECK_OPTION(GET, argv[i])){
-			curr->operation |= OP_GET;
-			continue;
-
-		}else if(CHECK_OPTION(FADE, argv[i])){
-			CHECK_NEXT_ARG(-5);
-			curr->fade_duration = strtol(argv[++i], NULL, 0);
-			continue;
-		}
-
-		else if(CHECK_OPTION(DEVICE, argv[i])){
-			CHECK_NEXT_ARG(-5);
-			curr->next = calloc(1, sizeof(struct arg_values));
-			curr = curr->next;
-			curr->device = argv[++i];
-			continue;
-		}
-		else if(CHECK_OPTION(HELP, argv[i])){
-			free_cmd_args(&ret);
-			usage(0);
-		}
-
-		//If we get a '-' followed by not a number, it's not a known option
-		else if(argv[i][1] < '0' || argv[i][1] > '9'){
-			UNRECOGNIZED_OPTION(-4);
-		}
-
-		//If we get a '-' followed by a number, it's a decrement request
-		else{
-			switch(argv[i][0]){
-				case '=':
-					curr->operation = OP_SET;
-					break;
-				case '-':
-					curr->operation = OP_DEC;
-					break;
-				case '+':
-					curr->operation = OP_INC;
-					break;
-				default:
-					UNRECOGNIZED_OPTION(-4);
-			}
-			curr->delta = atof(&argv[i][1]);
-		}
 	}
-
-	//If there isn't an operation defined in the global context and there is no specified device, there's nothing to do
-	if(!ret.operation){
-		if(!ret.next){
-			fprintf(stderr, "No operation requested!\n\n");
-			usage(-1);
-		}
-		//if there is a device specified, make sure each one has a requested operation
-		for(curr = ret.next;curr;curr = curr->next){
-			if(!curr->operation){
-				fprintf(stderr, "No operation requested for device '%s'!\n\n", curr->device);
-				usage(-1);
-			}
-		}
-	//If there is a globally defined operation, apply it to the devices with no operation request
-	}else{
-		for(curr = ret.next;curr;curr = curr->next){
-			if(!curr->operation)
-				curr->operation = ret.operation;
-		}
-	}
-	return ret;
+	fprintf(bright, "%d", out);
+	fclose(bright);
 }
-#undef CHECK_OPTION
-#undef UNRECOGNIZED_OPTION
 
 //argv[1] shall be [+-=]<percentage>|min|max|off
 int main(int argc, char** argv){
-	const char* backlight_file = "brightness";
-	const char* max_backlight_file = "max_brightness";
 
-	struct arg_values args = process_cmd_args(argc, argv);
+	struct arg_values args; //A linked list of devices and the requested settings.
+	struct string_array backlight_names; //List of all backlight devices in sysfs.
 
-	//Acquire a list of backlight devices in sysfs
-	struct string_array backlight_names = get_backlight_sources();
+	args = process_cmd_args(argc, argv);
+	backlight_names = get_backlight_sources();
+
+//Macro for easy memory cleaning
+#define CLEANUP() do{free_string_array(&backlight_names);free_cmd_args(&args);}while(0)
+
+
+
+	//If there are no backlights, we can't do anything
 	if(backlight_names.size == 0){
 		fprintf(stderr, "No backlights devices found!\n");
-		return -1;
+		CLEANUP();
+		return RETVAL_INVALID_DEVICE;
+	}
+
+	//Make sure all explicit devices actually exist
+	for(struct arg_values* curr = args.next;curr;curr = curr->next){
+		for(int i = 0;i < backlight_names.size;i++){
+			if(!strcmp(curr->device, backlight_names.list[i])){
+				goto continue_outer;
+			}
+		}
+		fprintf(stderr, "No such device '%s'\n", curr->device);
+		CLEANUP();
+		return RETVAL_INVALID_DEVICE;
+		continue_outer:;
 	}
 
 	//save our starting directory so we can change to each backlight directory (makes logic easier)
 	char* starting_dir = getcwd(NULL, 0);
 
+//Redefine CLEANUP to include freeing of the starting_dir string
+#undef CLEANUP
+#define CLEANUP() do{free_string_array(&backlight_names);free_cmd_args(&args);free(starting_dir);}while(0)
+
+	//Change to the base directory for all sysfs backlights
 	if(chdir(backlight_dir)){
 		fprintf(stderr, "Unable to read backlight sysfs directory!\n");
-		return -2;
+		CLEANUP();
+		return RETVAL_INVALID_DIR;
 	}
 
-	//Set all backlight sources to the requested percentage
-	for(int i = 0;i < backlight_names.size;i++){
-		if(chdir(backlight_names.list[i])){
-			fprintf(stderr, "Unable to open backlight directory \"%s%s\"!\n", backlight_dir, backlight_names.list[i]);
-			continue;
+	//If args.next is not NULL, then 1+ devices were specified. Only apply change to those
+	if(args.next){
+		for(struct arg_values* curr = args.next;curr;curr = curr->next){
+			if(chdir(curr->device)){
+				fprintf(stderr, "Unable to open backlight directory \"%s%s\"!\n", backlight_dir, curr->device);
+				continue;
+			}
+			write_delta(curr->delta);
 		}
-
-		//Write value to backlight files
-		int out = process_arg(argv[1], 0, get_brightness(backlight_file), get_brightness(max_backlight_file));
-		FILE* bright = fopen(backlight_file, "w+");
-		if(!bright){
-			fprintf(stderr, "Unable to open brightness file \"%s%s\" for writing!\n", backlight_dir, backlight_file);
-			continue;
+	//Otherise, apply delta to all backlights
+	}else{
+		for(int i = 0;i < backlight_names.size;i++){
+			if(chdir(backlight_names.list[i])){
+				fprintf(stderr, "Unable to open backlight directory \"%s%s\"!\n", backlight_dir, backlight_names.list[i]);
+				continue;
+			}
+			write_delta(args.delta);
 		}
-		fprintf(bright, "%d", out);
-
-		fclose(bright);
 	}
-	free_string_array(&backlight_names);
-	free_cmd_args(&args);
 	//Return to start directory
 	if(chdir(starting_dir)){
-		free(starting_dir);
+		CLEANUP();
 		fprintf(stderr, "Could not return to starting directory!\nWas the directory moved/deleted?\n");
-		if(chdir(getenv("HOME")) || chdir("/")){
-			return -5;
+		if(!chdir(getenv("HOME")) || !chdir("/")){
+			return RETVAL_INVALID_DIR;
+		}else{
+			return RETVAL_INVALID_DIR;
 		}
 	}
-	free(starting_dir);
-	return 0;
+	CLEANUP();
+	return RETVAL_SUCCESS;
 }
+#undef CLEANUP